VCA and oscillator

[Dimitree]

Hi everyone
maybe this is more synth-related, but I guess many of you know that better.
I was looking at this schematic (just for learning purposes):



I have some questions:
1) is this a VCA?
2) what would we expect on the output (using that input described)?
3) what the 4 variable resistors adjust?
4) does the Depth input allow for 0V to 5V values?

many thanks to everyone

[frequencycentral]

Looks like a wavefolder to me. Where is the schematic from?

[Dimitree]

actually I don't know, it came from my notes, and I remember that I never understood how it worked and what it did, so I asked. As for my notes, it should output the same waves from input, but with 2V minimum voltage and 4V maximum voltage, and with a smoothed bottom

[PRR]

It is a piece of a larger problem that you don't want to have.

Someone had a VCA which was more sensitive to negative swing than positive swing. Maybe a log amp, maybe a simple device.

When fed with a linear sine or triangle wave it did not give symmetric change of gain.

The front amp allows depth control. It has some DC shift so there's several levels of compensation.

The middle amp is a simple wave-shaper which reduces positive swings.

The last amp inverts so the negative swings are reduced, also reduces overall level, and injects bias.

If that does not make sense, be happy. I think if I found myself doing all this, I'd try to find a different VCA technology which worked to my liking without a mess of analog computation in front.

[Dimitree]

thank you for the response
sorry I'm not english so maybe I didn't get it all, what you mean with: more sensitive to negative swing? the input is 0-5V so there should not be negative swings, am I wrong?
do you think it is right that this circuit would put out a wave within the 2V and 4V range (starting from 0V/5V)?
and if depth control is 0V, what would it happen?